细胞膜结构域的光热共振成像和光谱研究
Imaging and Spectroscopy of Domains of the Cellular Membrane by Photothermal-Induced Resonance
摘要：
我们使用光热诱导共振（PTIR）成像和光谱，在共振和非共振模式，研究完整细胞的细胞质膜和表面。非共振PTIR图像显然提供了细胞表面的丰富细节。然而，我们表明，非共振图像对比度不会产生从表面分子的红外吸收，而是由针尖-样品接触的力学为主。相比之下，细胞表面的光谱和图像可以通过调整激光器的脉冲结构来限制热波穿透到表面层来选择性地获得。共振PTIR图像揭示了尺寸范围从约20 nm至1 μ m的表面结构和域，并且与细胞质膜及其邻近区域相关。细胞表面的共振PTIR光谱与远场IR光谱相当，并且提供完整细胞的细胞膜的IR吸收光谱的第一选择性测量。在共振PTIR图像中，信号强度以及因此的对比度可以归因于多种因素，包括细胞表面的机械、热力学和光谱特性。虽然PTIR图像难以在光谱吸收方面进行解释，但它们易于收集并提供独特的对比机制，而无需任何外源标记。因此，他们提供了一个新的范例，在细胞成像和膜生物学，并可用于解决一系列关键问题，从膜脂质结构域的性质，病毒膜融合。
英文摘要：
We use photothermal induced resonance (PTIR) imaging and spectroscopy, in resonant and non-resonant mode, to study the cytoplasmic membrane and surface of intact cells. Non-resonant PTIR images apparently provide rich details of the cell surface. However we show that non-resonant image contrast does not arise from the infrared absorption of surface molecules and is instead dominated by the mechanics of tip-sample contact. In contrast, spectra and images of the cellular surface can be selectively obtained by tuning the pulsing structure of the laser to restrict thermal wave penetration to the surface layer. Resonant PTIR images reveal surface structures and domains that range in size from about 20 nm to 1 um and are associated to the cytoplasmic membrane and its proximity. Resonant PTIR spectra of the cell surface are comparable to far-field IR spectra and provide the first selective measurement of the IR absorption spectrum of the cellular membrane of an intact cell. In resonant PTIR images, signal intensity, and therefore contrast, can be ascribed to a variety of factors, including mechanical, thermodynamic and spectroscopic properties of the cellular surface. While PTIR images are difficult to interpret in terms of spectroscopic absorption, they are easy to collect and provide unique contrast mechanisms without any exogenous labeling. As such they provide a new paradigm in cellular imaging and membrane biology and can be used to address a range of critical questions, from the nature of membrane lipid domains to viral membrane fusion.
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